Superbrasvie Tools Containing Uniformly Leveled Superabrasive Particles and Associated Methods

ABSTRACT

A superabrasive tools having uniformly leveled superabrasive particles and associated methods are provided. In one aspect, for example, a superabrasive can include a metal matrix configured for bonding superabrasive particles and a plurality superabrasive particles held in the metal matrix at specific positions according to a predetermined pattern, wherein tips of each of the plurality of the superabrasive particles protrude from the metal matrix to a uniform height.

PRIORITY DATA

This application is a continuation of U.S. patent application Ser. No.12/463,897, filed on May 11, 2009, which is a continuation of U.S.patent application Ser. No. 11/818,894, filed on Jun. 14, 2007, which isa continuation of U.S. patent application Ser. No. 10/791,300, filedMar. 1, 2004, now issued as U.S. Pat. No. 7,323,049, which is acontinuation-in-part of U.S. patent application Ser. No. 10/259,168,filed Sep. 27, 2002, now issued as U.S. Pat. No. 7,124,753, which is acontinuation-in-part of U.S. patent application Ser. No. 09/935,204,filed Aug. 22, 2001, now issued as U.S. Pat. No. 6,679,243, and of U.S.patent application Ser. No. 10/109,531, filed Mar. 27, 2002, now issuedas U.S. Pat. No. 6,884,155. U.S. Pat. No. 6,679,243 is acontinuation-in-part of U.S. patent application Ser. No. 08/835,117,filed on Apr. 4, 1997 and a continuation-in-part of U.S. patentapplication Ser. No. 09/399,573, filed Sep. 20, 1999, now issued as U.S.Pat. No. 6,286,498, which is a continuation-in-part of U.S. patentapplication Ser. No. 08/832,852, filed Apr. 4, 1997, now abandoned. U.S.Pat. No. 6,884,155 is a continuation-in-part of U.S. patent applicationNo. 09/588,582, filed Apr. 26, 2000, now issued as U.S. Pat. No.6,368,198, which is a continuation-in-part of U.S. patent applicationNo. 09/447,620, filed Nov. 22, 1999, now abandoned, all of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

Diamonds and cubic boron nitride (CBN) have been widely used assuperabrasives on saws, drills, and other tools which utilize thesuperabrasive to cut, form or polish other hard materials. In 1996, thetotal value of superabrasive tools consumed was over 5 billion dollars(U.S.). It has been estimated that more than half of the superabrasivetools were consumed in sawing applications such as cutting stones,concretes, asphalts, etc.

Diamond tools are particularly indispensable for applications whereother tools lack the strength and durability to be practicalsubstitutes. For example, in the stone industry where rocks are cut, orsawed, diamond saws are the type that are sufficiently hard and durableto do the cutting. If superabrasives were not used, many such industrieswould be economically infeasible. Likewise, in the precision grindingindustry, superabrasive tools, due to their superior wear resistance,are uniquely capable of developing the tight tolerances required, whilesimultaneously withstanding wear sufficiently to be practical.

Despite the tremendous improvements which diamond and cubic boronnitride have provided for cutting, drilling and grinding tools, thereare still several disadvantages which, if overcome, would greatlyimprove performance of the tools, and/or reduce their cost. For example,the abrasive diamond or cubic boron nitride particles are notdistributed uniformly in the matrix that holds them in place. As aresult, the abrasive particles are not positioned to maximize efficiencyfor cutting, drilling, etc.

The distance between diamond or CBN abrasive particles determines thework load each particle will perform. Improper spacing of the diamond orCBN abrasive particles typically leads to premature failure of theabrasive surface or structure. Thus, if the diamond/CBN abrasiveparticles are too close to one another, some of the particles areredundant and provide little or no assistance in cutting or grinding. Inaddition, excess particles add to the expense of production due the highcost of diamond and cubic boron nitride. Moreover, these non-performingdiamond or CBN particles can block the passage of debris, therebyreducing the cutting efficiency. Thus, having abrasive particlesdisposed too close to one another adds to the cost, while decreasing theuseful life of the tool.

On the other hand, if abrasive particles are separated too far, the workload (e.g., the impact force exerted by the work piece) for eachparticle becomes excessive. The sparsely distributed diamond or CBNabrasive particles may be crushed, or even dislodged from the matrixinto which they are disposed. The damaged or missing abrasive particlesare unable to fully assist in the work load. Thus, the work load istransferred to the surviving abrasive particles. The failure of eachabrasive particle causes a chain reaction which soon renders the toolineffective to cut, drill, grind, etc. A typical superabrasive tool,such as a diamond saw blade, is manufactured by mixing diamond particles(e.g., 40/50 U.S. mesh saw grit) with a suitable matrix (bond) powder(e.g., cobalt powder of 1.5 micrometer in size). The mixture is thencompressed in a mold to form the right shape (e.g., a saw segment). The“green” form is then consolidated by sintering at a temperature between700-1200° C. to form a single body with a plurality of superabrasiveparticles disposed therein. Finally, the consolidated body is attached(e.g., by brazing) to a tool body; such as the round blade of a saw, toform the final product.

Different applications, however, require different combinations ofdiamond (or cubic boron nitride) and matrix powder. For example, fordrilling and sawing applications, a large sized (20 to 60 U.S. mesh)diamond grit is mixed with a metal powder. The metal powder is typicallyselected from cobalt, nickel, iron, copper, bronze, alloys thereof, and/or mixtures thereof. For grinding applications, a small sized (60/400U.S. mesh) diamond grit (or cubic boron nitride) is mixed with eithermetal (typically bronze), ceramic/glass (typically a mixture of oxidesof sodium, potassium, silicon, and aluminum) or resin (typicallyphenolic, or polyemide).

Because diamond or cubic boron nitride is much larger than the matrixpowder (300 times in the above example for making saw segments), and itis much lighter than the latter (about ⅓ in density for making sawsegments), it is very difficult to mix the two to achieve uniformity.Moreover, even when the mixing is thorough, diamond particles can stillsegregate from metal powder in the subsequent treatments such as pouringthe mixture into a mold, or when the mixture is subjected to vibration.The distribution problem is particularly troublesome for making diamondtools when diamond is mixed in the metal matrix. Thus, finding a methodfor increasing the performance of the diamond or CBN superabrasivematerial, and/or decreasing the amount of the abrasive which is needed,is highly desirable. Such has been accomplished by the invention setforth herein. The invention is particularly effective and useful fordiamond saws, the largest value category of all superabrasive tools,although it is applicable to all abrasive tools.

Over the decades, there have been numerous attempts to solve the diamondor CBN distribution problems. Unfortunately, none of the attemptedmethods have proven effective and, as of today, the distribution ofdiamond or CBN particles in superabrasive tools is still random andirregular, except for some special cases such as for drillers ordressers, where large diamond particles are individually set by hand inthe surface to provide a single layer.

One method used in an attempt to make the diamond distribution uniformis to wrap diamond particles with a thick coating of matrix powder. Theconcentration of diamond particles in each diamond tool is tailored fora particular application. The concentration determines the averagedistance between diamond particles. For example, the concentration of atypical saw segment is 25 (100 means 25% by volume) or 6.25% by volume.Such a concentration makes the average diamond to diamond distance 2.5times the particle size. Thus, if one coats the diamond and mixes thecoated particles together, the distribution of diamond would becontrolled by the thickness of coating and may become relativelyuniform. Additional metal powder may be added as an interstitial fillerbetween these coated particles to increase the packing efficiency so theconsolidation of the matrix powder in subsequent sintering would beeasier. Although the above-described coating metal has certain merit, inpractice, uniformity of coating is very difficult to achieve.

There is yet another limitation associated with the current methods ofcoating diamond grits. Many times a metal bond diamond tool requiresdifferent sizes of diamond grits and/or different diamond concentrationsto be disposed at different parts of the same diamond tool. For example,saw segments tend to wear faster on the edge or front than the middle.Therefore, higher concentrations are preferred in these locations toprevent uneven wear and thus premature failure of the saw segment. Thesehigher concentration (known as “sandwich” segments) are difficult tofabricate by mixing coated diamond with metal powder to achieve acontrolled distribution of the diamond particles in the segment. Thus,despite the known advantages of having varied diamond grit sizes andconcentration levels, such configurations are seldom used because of thelack of a practical method of making thereof. In summary, current artsare incapable of efficiently controlling the uniformity of diamond orCBN distribution in cutting tools. Likewise, the current methods areinadequate to provide effective control of size variations and/orconcentration variations on different parts of the same tool. Moreover,even when the distribution is made relatively uniform, current artscannot tailor the pattern of the distribution to overcome or compensatefor typical wear patterns for the abrasive material, when used for aparticular purpose. By resolving these problems, the performance of adiamond and other superabrasive tools can be effectively optimized.

This invention provides significant improvements to overcome thedeficiencies. discussed above by eliminating random distribution ofsuperabrasive particles. This invention provides a superabrasive inwhich every diamond or CBN particle is positively planted at desiredpositions to achieve the maximum utility of the superabrasive particles.Hence, the performance of the superabrasive tool can be optimized.

By making the distribution of diamond or CBN particles, uniform or in apredetermined pattern and tailored to the particular applications of thetool, the work load can be evenly distributed to each particle. As aresult, the superabrasive tool will cut faster and its working life willbe extended for a considerable amount of time. Moreover, by eliminatingthe redundancy, less superabrasive may be needed, thereby reducing thecost of the tool manufacture. Additionally, if the distribution can becontrolled, superabrasive tools utilizing diamond or cubic boron nitridecan be configured to provide the most efficient tool possible.

The present invention resolves these problems and provides theadvantages set forth above by providing a method for forming such metalbond diamond or CBN tools wherein the superabrasive grit distributioncan be controlled to provide either uniform grit placement, or toprovide a grit placement pattern which is tailored to the particularwear characteristics of the tool. Because the distribution of thediamond/CBN grits is controlled, the diamond/CBN grits can be disposedin patterns which provide for relatively even wear of the abrasivesurface, rather than having portions of the surface wear prematurely. Aseach superabrasive grit is more fully utilized, there is no need forredundant superabrasive grits as a backup. Therefore, the cost of makingthe metal bond diamond or CBN tools can be reduced by reducing theoverall amount of superabrasives.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method for formingmetal bond superabrasive tools, wherein the distribution of thesuperabrasive grit is monitored to provide improved cutting, sawing, orgrinding, characteristics without requiring an increase in the amount ofsuperabrasive grit used to form the tool.

It is another object of the invention to provide such a method whereinthe distribution of the superabrasive grit is controlled to promote moreeven wear of the tool surface, and thereby lengthen the useful life ofthe tool.

It is yet another object of the present invention to provide tools withthe minimal amount of superabrasive required to perform the task forwhich the tool is designed, thereby reducing the cost of making thetool.

The above and other objects of the invention are achieved by providingmetal bond superabrasive tools wherein the superabrasives, such asdiamond or CBN grits, are distributed in a metal matrix in a uniform ora predetermined pattern. While the process of distributing diamond orcubic boron nitride grits in a metal matrix has always been viewed as acomplex one and needs to be improved, the present invention providessuch an improved process that is easy to manipulate and control, andwhich can be repeated with a high degree of accuracy. More specifically,the desire distribution of superabrasive particles in a metal matrixbody is achieved by assembling layers of metal matrix material thatcontain a controlled, predetermined pattern of superabrasive particles.Each layer is formed by distributing the superabrasive grit into a layerof bonding metal matrix in a predetermined pattern. Each layer, which isassembled to form a superabrasive impregnated segment, can be of thesame distribution pattern and concentration, or the distribution patternand/or concentration may vary from layer to layer.

In accordance with one aspect of the present invention, each layer isassembled by disposing a layer of metal matrix so that it may be used asa precursor. The superabrasive grit is then disposed in the metal matrixlayer in a desired pattern. After the diamond particles are planted intothe metal matrix layer in a predetermined pattern, the process isrepeated until a desired number of layers have been formed. These layersare then assembled to form the desired three-dimensional body.Subsequently the diamond tool is consolidated (e.g., by sintering orinfiltration as described above) to form the final product.

By assembling layers of metal matrix impregnated with superabrasives ina predetermined pattern and concentration into a three dimensional body,the present invention not only provides the desirable diamond/CBNdistribution pattern in the tool body, but also provides the flexibilityfor possible manipulation of diamond concentration at different parts ofthe same tool body. Thus, for example, diamond particles can be disposedin denser concentrations in some layers than others, and the layers withthe greater diamond/CBN concentrations can be disposed within thethree-dimensional structure created in such a manner as to prevent theuneven wear patterns that are typical in many prior art diamond tools.

In accordance with another aspect of the present invention each metalmatrix layer impregnated with superabrasives is created by first forminga thin layer of metal bonding matrix. A template is then disposed on themetal bonding matrix. The template has a plurality of apertures formedtherein which are sized to receive a superabrasive grit of a particularsize, with one particle being disposed in each aperture. As thesuperabrasive grit fills the apertures, the grits may be subjected topressure or otherwise moved into the metal bonding matrix. Because ofthe template, the superabrasive which enters the metal bonding matrix isdisposed in a predetermined pattern. A plurality of such metal matrixlayers impregnated with superabrasives can then be bonded together andattached to the tool by brazing, or some other process, to provide athree-dimensional superabrasive cutting or sawing member on the tool.

In accordance with another aspect of the present invention, the patternin which the superabrasive grit is disposed may be uniform, or may becalculated to provide superabrasive members with particular cutting orsawing abilities. For example, the superabrasive particles may bedisposed in varied concentrations to compensate for uneven wearpatterns. Thus, the diamond or CBN distribution for the cutting edge ofa saw may have a greater distribution of diamond or CBN particles in thelead edge and sides than in the middle portion which is generallysubjected to less wear. Likewise, the sizes of the superabrasiveparticles can be controlled to provide a cutting, grinding, etc.,surface which is tailored to the particular uses and wear patterns forthe tool.

Yet another aspect of the present invention is to mix diamond/CBN gritswith a metal powder in a conventional manner. However, instead ofpressing the mixture to form a body, the metal powder is glued with abinder and rolled to form a sheet or layer. In this case, althoughdiamond/CBN grits distribution does not form a predetermined pattern,the grit distribution is much more uniform than mixing metal powder withdiamond grits to form thick body by a conventional mixing process. Thelayers thus formed can then be stacked up to form the final body. Inthis case, powders are already locked in layers so they cannotsegregate.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the inventionwill become apparent from a consideration of the following detaileddescription presented in connection with the accompanying drawings inwhich:

FIG. 1A shows a segment from a superabrasive tool formed by a pluralityof linear, longitudinal layers disposed adjacent one another to form athree-dimensional superabrasive member;

FIG. 1B shows a cross-sectional view of one likely configuration of thetool segment shown in FIG. 1A, wherein a layer formed by a metal matrixand a relatively large superabrasive grit is sandwiched between twolayers of metal matrix which have smaller grit and higher concentrationsof the superabrasive;

FIG. 2A shows a segment from a superabrasive tool formed by a pluralityof arcuate, longitudinal layers which are attached to one another toform a three-dimensional superabrasive member;

FIG. 2B shows a cross-sectional view of a plurality of layers of metalmatrix as may be used with the segment shown in FIG. 2A;

FIG. 3 shows another possible layout of a segment of a cutting tool withtransverse layers configured with a more dense or higher concentrationof superabrasive grits disposed at a forward, cutting end of thethree-dimensional superabrasive member;

FIG. 4 shows yet another layout of a segment wherein a three-dimensionalsuperabrasive member is formed with progressively denser abrasivedistribution toward the upper surface of a tool with horizontal layers;

FIGS. 5A through 5D show one possible method for forming layers withcontrolled superabrasive distribution within the layer;

FIGS. 6A through 6C shows an alternate method for forming one or morelayers with controlled superabrasive distribution.

DETAILED DESCRIPTION

Before the present invention comprising metal bond diamond tools thatcontain uniform distribution of diamond grits and the method for themanufacture thereof is disclosed and described, it is to be understoodthat this invention is not limited to the particular process steps andmaterials. In disclosing and claiming the present invention, thefollowing terminology will be used in accordance with the definitionsset out below.

As used herein, the terms set herein as such process steps and materialsmay vary somewhat. It is also to be understood that the terminologyemployed herein is used for the purpose of describing particularembodiments only and is not intended to be limiting since the scope ofthe present invention will be limited only by the appended claims andequivalents thereof.

It must be noted that, as used in this specification and the appendedclaims, the singular forms “a,” “an,” and “the” include plural referentsunless the context clearly dictates otherwise. Thus, for example,reference to a metal bond diamond containing “a diamond grit” includes amixture of two or more diamond grits, reference to “a superabrasive”includes reference to one or more of such superabrasives, and referenceto “a metal” includes reference to a mixture of two or more of suchmetals. “Diamond grit” and “superabrasive grit” are used interchangeablyin this application, and include diamond, CBN, or other superabrasivegrits.

“Grit”and “particle” are used interchangeably in this application,referring to particles which is significant larger than a powder,usually with a size of at least 400 U.S. mesh (40 micrometer). “Metalbond diamond tools” refers to superabrasive tools wherein thesuperabrasives are diamond or other superabrasives such as CBN grits ofa size larger than 400 U.S. mesh, and the grits are bonded by a metalmaterial. Metal bond diamond tools usually include diamond saws, diamonddrill bits, diamond dressers, and diamond grinding wheels. Metal bonddiamond saws with uniform or patterned distributed diamond grits of thepresent invention include wire saws with diamond beads, circular sawswith diamond segments, chain saws with diamond segments, and frame(reciprocating) saws with diamond segments. Except for the diamondgrinding wheels, polishing, and lapping tools that contain diamond gritssmaller than 60 mesh, all other metal bond diamond tools contain diamondgrits larger than 60 mesh.

References will now be made to the drawings in which the variouselements of the present invention will be given numeral designations andin which the invention will be discussed so as to enable one skilled inthe art to make and use the invention. It is also understood that thefollowing description is only exemplary of the principles of the presentinvention, and should not be viewed as narrowing the pending claims.

Referring to FIG. 1A, there is shown a perspective view of a segment,generally indicated at 10, from a metal bond superabrasive tool (theremainder of which is not shown). The segment 10 is formed by aplurality of layers, 14, 16, and 18, which are impregnated withsuperabrasive grits, indicated by the dark circles 20. The plurality oflayers 14, 16 and 18 are disposed adjacent to one another in a linear,longitudinal array so that the layers form the three-dimensionalsuperabrasive segment 10.

As will be discussed in additional detail below, forming the segment 10in a plurality of thin layers provides remarkably improved control overthe distribution of the superabrasive grits. By controlling thedistribution of the superabrasive grits within each layer and thencombining the layers, a three-dimensional segment can be formed in whichthe distribution of the superabrasive grits is controlled in eachdimension. This, in return, enables the formation of segments which areparticularly adapted to the intended use of the segment, such ascutting, sawing, grinding, etc. By tailoring the distribution andconcentration of the superabrasive grits within the segment 10, moreprecise control is given over performance of the tool under actualworking conditions.

For example, when using a diamond saw blade to cut rocks (e.g.,granite), the two sides of the diamond saw segments are cutting morematerials than the center. As the result of uneven wear, the crosssection of the saw segment becomes convex in shape with the centerbulging above both sides. This configuration typically slows the cuttingrate of the saw blade. Moreover, the protruding profile may also causethe saw blade to deflect sideways in the cut slot. In order to maintaina straight cutting path, it is sometimes desirable to make a “sandwichdiamond segment” to reinforce both sides of the segment with layersimpregnated with more diamond or superabrasive grits. Such a “sandwichsegment” is difficult to manufacture by mixing diamond grit with metalpowder by conventional means, but it can be easily accomplished bymethods of the present invention: first planting diamond grits withdesirable patterns and concentrations in a metal matrix layer and thenassembling these metal matrix layers with diamond grits impregnated inthe predetermined patterns and concentrations together to form asandwiched segment.

In accordance with the present invention, a cutting segment can beformed to resist premature wear to the sides of the segment, therebyextending the cutting segment's useful life. Referring specifically toFIG. 1B, there is shown a cross-sectional view of the cutting segment 10of FIG. 1A. Unlike the cutting segments of the prior art, the cuttingsegment 10 is formed of three layers, 14, 16 and 18 respectively. Themiddle layer 16 has a plurality of superabrasive grits 20 a of a firstsize (typically 40/50 U.S. mesh) and a first concentration (e.g. 20).The outer layers 14 and 18, in contrast, have a plurality ofsuperabrasive grits 20 b, which are of a second size (typically 50/60U.S. mesh), smaller than the first size, and in a second concentrationwhich is greater than that present in the middle layer 16 (e.g. 23). Thesmaller, more densely distributed superabrasive grits 20 b provide theouter layers 14 ad 18 with a greater resistance to wear as they cutthrough concrete, rock, asphalt, etc. Because the outer layers 14 and 18are more wear resistant, the cutting segment 10 avoids problem offormation of a convex outer surface, as has traditionally occurred withconventional cutting tools. By maintaining a more planar cutting surfaceor even a concave profile, the cutting segment of the present inventioncan maintain a straighter cutting path and have a longer useful life.Moreover, by using a smaller grit on the flank of the saw, the finish ofthe cut surface is smoother. Furthermore, chipping of the workpiece canbe avoided.

Another advantage to the use of multiple layers of metal matriximpregnated with diamond or cubic boron nitride particles is that thelayers are easily formed into other desirable shapes. For example, FIG.2A shows a perspective view of a saw segment, generally indicated as 30,of a superabrasive tool formed by a plurality of arcuate, longitudinallayers which are attached to one another to form a three-dimensionaltool member. In this example, the segment 30 is formed from first,second and third layers, 34, 36, and 38, each of which are arcuate. Whenthe three are joined together, an arcuate segment 30 is created. Such asegment, of course, may be used on cutting tools for and on other typesof tools for which a nonlinear superabrasive segment is desired. Becausethe layers 34, 36 and 38 are initially formed independent of oneanother, they are much easier to conform to a desired shape, and areable to made so while the superabrasive particles 20 disposed thereinare held in their predetermined positions.

Each of the layers shown in the drawings is impregnated with a pluralityof superabrasive particles 20, typically diamond or cubic boron nitride.Because each layer is a relatively thin layer of metal matrix, (i.e.,the metal matrix is usually no more than two times the thickness of thediameter of the particles), superior control over placement of thesuperabrasive particles in the metal matrix layer can be easilyachieved. As discussed above, the random placement of superabrasives intools in the current art often lead to ineffective use of superabrasiveparticles. By controlling distribution of superabrasives the presentinvention enables either even distribution which prevents under or overspacing, or controlled distribution so that different portions of thesegment have different sizes and concentrations which are matched toprevent traditional wear patterns.

Referring now to FIG. 2B, there is shown a cross-sectional view of aplurality of the layers 34, 36 and 38 of the segment 30. Of course, thesuperabrasive particle may be used with the segment shown in FIG. 1A orFIG. 2A. Unlike the embodiment of FIG. 1B, the layers are each providedwith the same size and concentration of the superabrasive particles 20.However, because the spacing is essentially uniform, there is nounderspacing or overspacing between the superabrasive particles, and thesegment 30 wears more evenly than the segments of the prior art withtheir randomly spaced particles. The more even wear prevents prematurefailure of the segment 30, and thus extends the life of the tool whilekeeping the amount of superabrasive used to a minimum.

FIG. 3 shows another possible embodiment of a segment 50 made inaccordance with the method of the present invention. The layeredstructure in a diamond or CBN segment may also be assembled transverselyor horizontally. Thus, the segment 50 in FIG. 3 is formed from aplurality of transverse layers, generally indicated at 54. A firstplurality of layers, indicated at 56 are provided with a firstconcentration of superabrasive particles 20 (represented by four layers,that contain superabrasive particles 20 distributed within an offsetpattern). A second plurality of layers, indicated at 58, are providedwith a second concentration, less than the first concentration(represented by nine layers with an offset pattern of superabrasiveparticles 20).

Many cutting tools are configured such that the cutting segment isprovided with a lead edge which performs a majority of the cutting andwhich receives most of the impact force when contacting the workpiece tobe cut. For example, a circular saw blade will usually have a pluralityof teeth (saw segments), each tooth having a leading edge which takesthe force of the cutting. Because the leading edge performs asignificant portion of the cutting, it is much more susceptible to wearthan are the rotationally trailing portions of the tooth. When formed inaccordance with the prior art, the teeth, however, often had similarconcentrations of abrasive particles disposed therein. Over time theleading edge wears significantly, but the trailing layers remain withminimal wear. Eventually, the abrasive of the saw tooth is worn off theleading edge, while significant amounts remain on the tail end. Thus, aconsiderable amount of superabrasive is wasted when the blade isdiscarded.

The embodiment of FIG. 3 is specifically configured to overcome suchconcerns. The layers 56 and 58 are configured to provide substantiallyeven wear across the cutting segment 50 by placing a larger percentageof the superabrasive particles 20 near the leading edge layers 56, thanon rotationally distal portions 58. Thus, by the time the leading edge56 has reached the end of its useful life, the remaining portions 58 ofthe cutting segment 50 may also be worn out. Such controlleddistribution of the superabrasive particles 20 decreases the use of theexpensive material and lowers the cost for making the cutting segment 50without impeding performance. Additionally, by providing more ever wear,the cutting segment 50 will often be able to maintain most of itscutting speed until shortly before the end of its useful life.

FIG. 4 shows yet another layout of a segment 70 wherein athree-dimensional superabrasive member is formed with progressivelydenser abrasive distribution toward the upper surface of a tool withhorizontal layers. It is often found that the speed of cutting tends todecrease with the wear of the tool. Thus, with a reduced concentrationof superabrasive particles, the tool can maintain its current cuttingspeed at a constant power of the machine. Thus, as with the embodimentof FIG. 3, the controlled distribution of the superabrasive particles 20forms an improved abrasive segment 70, while at the same time decreasingthe cost of abrasive tools by saving those superabrasive particles whichare not needed.

With routine experimentation and the teachings of the method of thepresent invention, those skilled in the art will be able to customizecutting, drilling, grinding, polishing and other types of abrasivesegments which are specifically formed to maximize their performance(i.e, cutting, drilling, grinding, etc.) over an extended useful life,while simultaneously decreasing the amount of expensive superabrasivewhich is used to form the tool.

Referring now to FIGS. 5A through 5D, there is shown one method forforming layers in accordance with the principles of the presentinvention. The first step of the method is to form a sheet 100 of matrixmaterial 104 which will be bonded to the superabrasive particles 20. Thesheet 100 of matrix material 104 can be formed from conventional metalpowders as discussed above, or of any other suitable bonding agents.

There are many ways that a metal matrix powder can be made into thesheets 100. For example, the powder can first be mixed with a suitablebinder (typically organic) and a solvent that can dissolve the binder.This mixture is then blended to form a slurry having a desiredviscosity. In order to prevent the powder from agglomerating during theprocessing, a suitable wetting agent (e.g., menhaden oil, phosphateester) may also be added. The slurry can then be poured onto a plastictape and pulled underneath a blade or leveling device. By adjusting thegap between the blade and the tape, the slurry can be cast into a sheetwith the right thickness. The tape casting method is a well known methodfor making thin sheets out of powdered materials and it works well withthe method of the present invention.

Alternatively, the metal powder can be mixed with a suitable binder andits solvent to form a deformable cake. The cake can then be extrudedthrough a die with slit opening. The gap in the opening determines thethickness of the extruded plate. Alternatively, the material can also bedrawn between two rollers with adjustable gap to form sheets with theright thickness.

It is desirable to make the sheets pliable for subsequent treatments(e.g., bending over a tool substrate which has a curvature). Therefore,a suitable organic plasticier may also be added to provide the desiredcharacteristics.

The use of organic agents for powder (metal, plastics, or ceramics)processing is documented in many text books and it is well known bythose skilled in the art. Typical binders include polyvinyl alcohol(PVA), polyvinyl butyral (PVB), polyethylene glycol (PEG), paraffin,phenolic resin, wax emulsions, and acrylic resins. Typical bindersolvents include methanol, ethanol, acetone, trichlorethylene, toluene,etc. Typical plasticizers are polyethylene glycol, diethel oxalate,triethylene glycol, dihydroabietate, glycerine, octyl phthalate. Theorganic agents so introduced are used to facilitate the fabrication ofmetal layers. They must be removed before the consolidation of metalpowders. The binder removal process (e.g., by heating in a furnace withatmospheric control) is also well known to those skilled in the art.

Once the sheet 100 of matrix material 104 is formed, a template 110 islaid on the top of the sheet. The template 110 contains apertures 114that are larger than one abrasive particle 20, but smaller than twoabrasive particles, thereby allowing a single particle so of theabrasive to be disposed at each specific location.

In this example, the thickness of the template is preferably between ⅓to ⅔ of the diameter of the average abrasive particle 20. However, otherthicknesses may be used if appropriate accommodations are made forseating the abrasive particles in the desire locations.

After the template 110 is properly positioned, a layer of abrasiveparticles 20 is then spread over the template so that each aperture 114receives an abrasive particle. Those particles not falling into theapertures 114 in the template 110 are removed by tilting the substrate,sweeping the template with a brush, or some other similar method.

As shown in FIG. 5B, a generally flat surface 120, (such as a steelplate) is then laid over the particles 20 which rest in the apertures114 in the template 110. The flat surface 120 presses the abrasiveparticles 20 at least partially into the pliable sheet 100 of matrixmaterial 104 to seat the particles.

After removing the template 110, the flat surface 120 is used again topress the abrasive particles 120 firmly into the sheet 100 of matrixmaterial 104 as shown in FIG. 5C. While the flat surface 120 ispreferable, those skilled in the art will appreciate that there may beoccasions when it is desirable to have abrasive particles protrudingabove the metal sheet 100 with equal height. Alternatively, some of theabrasive particles 20 may want to be extended outward from the sheet 100of matrix material more than that of other abrasive particles. In suchsituations, a contoured or otherwise shaped surface could be used toseat some of the abrasive particles 20 deeper into the sheet 100 ofmatrix material 104, than other particles.

If desired, the process shown in FIGS. 5A through 5C can be repeated onthe other side of the sheet 100 of matrix material 104 (as shown in FIG.5D), to form an impregnated layer having abrasive particles 20distributed throughout the layer in some predetermined, desired pattern.The process is typically repeated several times to obtain multiple thinlayers or sheets 100 which are impregnated with the abrasive particles20. Of course, each sheet 100 needs not have the same distributionpattern for the abrasive particles 20, nor does it need theconcentration of the abrasive particles to be the same.

The abrasive impregnated sheets 100 are then cut to any desired size andshape. The sheets 100 are then assembled to form the tool segment or theentire tool body where appropriate. Typically, the assembly of thesheets 100 is accomplished by a known method such as cold compactionwith a press. The “green” body so formed can then be consolidated toform a final tool product by conventional methods of sintering orinfiltration as described by the following examples.

While the method described in FIGS. 5A through 5D is preferred for manyapplications, there are instances where it is desirable to have theabrasive particles 20 extend outwardly from the sheet 100 of matrixmaterial. For example, some tools may only have one layer of abrasive.This can be accomplished simply by leaving the template 110 in placewhen performing the steps shown in FIG. 5A and 5B, and not furtherpressing the particles 20 into the matrix material once the template hasbeen removed.

In the alternative, FIGS. 6A through 6C show a side view of an alternateto the method discussed in FIGS. 5A through 5D. The sheet 130 of matrixmaterial in FIGS. 6A through 6C is thinner than the height of thesuperabrasive particles 20. Thus, in this procedure, when the particlesare pressed into the sheet 130, the particles 20 would protrude abovethe matrix material 134.

The present invention is intended for making metal bond superabrasivetools containing superabrasives distributed in a predetermined threedimensional pattern, which provides a significant improvement over theprior art where the abrasives are typically random and non-uniformlydistributed. The methods illustrated in FIGS. 5A, the rough 6C offerseveral advantages over conventional technology. For example, by makingdiamond particles distributed in a desirable pattern, the load cuttingcan be evenly distributed to all diamond particles. As a result, thetool can cut faster and have a longer life.

The performance may be further improved by having a braze layer ofuniform thickness. This uniformity can allow a better diamond or CBNretention and easier debris removal. Moreover, by fully utilizing eachdiamond particle for cutting, the concentration of diamond can bereduced. As discussed, diamond cost often accounts for about half of thetotal manufacturing cost of a diamond tool. Hence, by practicing thisinvention, manufacturing cost can be reduced substantially.

Also shown in FIG. 6A through 6C is the principle that the spacings ofthe apertures in the template 130 need not be uniform. Rather,variations in spacing can be provided to facilitate differentconcentrations on various portions to facilitate differentconcentrations on various portions of the sheet 130 of matrix material134. Likewise, by controlling the size of the apertures 138 and theorder in which the diamond particles are placed in the apertures, asingle layer could be provided with particles of different sizes.

In addition to being able to improve the performance of the tool and toreduce the cost of manufacturing, this invention also provides an easiermethod for making thin bladed tools. For example, the electronicindustry requires using larger and larger silicon wafers (now 12 inchesin diameter). Hence, thinner saw blades for slicing silicon crystals,and thinner dicing wheels for grooving silicon chips with tighterpartitions have been in great demand.

Prior to the present invention, it has been extremely difficult to makevery thin tools that contain evenly distributed diamond particles. Thepresent invention provides an alternative method for making such tools.For example, it has been discovered that by mixing micron powders ofdiamond, a blend of metal powders (e.g., bronze and cobalt) and asuitable binder, the material can be rolled to a thickness thinner than0.1 mm—a thickness which is thinner than most dicing wheels. By firingthis thin sheet and mounting it on a tool holder, a thin dicing wheelcan be made.

In the alternative to the above, it has been found in accordance withthe present invention that some of the advantages of the controlleddistribution, multilayered superabrasive configurations described abovecan be achieved without the use of a template. More specifically, thesuperabrasive particles can also be mixed in with the matrix powder andmade as an ingredient of the layered sheet. In this case, thedistribution of abrasive particles are still somewhat random. Even so,their distribution is typically more uniform than that in a conventionalabrasive body. The segregation of superabrasive particles and matrixpowders discussed in the background section is less extensive in asubstantially two-dimensional sheet than in a three-dimensional body.This is particularly true for sheets made by a deforming process (e.g.,by rolling). In this case, superabrasive particles are further spreadout in the matrix by the shearing action of the rollers.

This invention may also be applicable to other applications not relatedto making abrasive tools. For example, graphite or metal sheets plantedwith diamond particles may be used as seeds for diamond growth underhigh pressure and temperature. Industrial diamonds are typicallyproduced by compressing alternative layers of graphite and metalcatalyst (e.g., Fe, Co, or Ni alloy) to high pressure and heating abovethe melting point of the catalyst. Diamond will then nucleate randomlyon the interface of these layers. The quality of the diamond crystalformed often suffers by the impingement of growing crystals that aredistributed unevenly. Hence, the yield and cost of diamond synthesis canbe substantially improved by making the nuclei uniformly distributed .This invention can provide layers of either graphite or metal catalystwith a pre-determined pattern of diamond seeds. If organic binders areintroduced during the fabrication of these layers, they can be removedby heating in a furnace before loading into the press.

The following are examples that illustrate preferred embodiments of theinvention but are intended as being representatively only.

Example 1

40/50 mesh diamond grit (SDA-85 made by De Beers Company) were mixedwith metal powder to form a mixture with a diamond concentration of 20(5% of total volume). Five different proportions of cobalt (about 1.5micrometer in size) and bronze (about 20 micrometers in size) were usedfor the matrix powder. An acrylic binder was added (8% by weight) to themixture and the charge was blended to form a cake. The cake was thenrolled between two stainless steel rollers to form sheets with athickness of 1 mm. These sheets were cut in the shape of saw segmentswith a length of 40 mm and width of 15 mm. Three each of such segmentswere assembled and placed into a typical graphite mold for makingconventional diamond saw segments. The assembled segments were pressedand heated by passing electric current through the graphite mold. Aftersintering for three minutes, the segments were consolidated to a heightof 9 mm with less then 1% porosity. Twenty-four segments for eachcomposition were fabricated. They were brazed onto a circular saw of 14inches in diameter. These blades were used for cutting granites andfound to perform equal or better than those with higher diamondconcentrations (e.g. 23) made by conventional methods. Microscopicexamination of the worn segment indicated that, although diamondparticles were not planted into the layered matrix, they weredistributed more evenly than segments prepared by the traditionalmethod. The segregation of particles in a layered matrix wasconsiderably less than that in the thick body of conventional segments.

Example 2

The same procedures were followed as Example 1, but with 8 thinnerlayers (0.4 mm) being used to form each segment. The diamondconcentration was reduced to 15 and particles were planted according tothe illustration as shown in FIGS. 5A through 5D, for each layer. Thediamond distribution was much improved. As a result, the performance ofthese blades were equal or better than those made by conventionalmethods with diamond concentration of 20.

Example 3

Iron powders of about 100 mesh were mixed with an S-binder made by WallColmonoy Company to form a cake. The cake was then rolled to form sheetsof 0.4 mm in thickness. 40/50 mesh SDA-100 diamond grit was planted intothese sheets to attain a concentration of 15. These diamond containingsheets were cut in the shape of saw segments with a length of 40 mm andwidth of 9 mm. Eight of such segments were assembled as a group andplaced in a graphite mold. Twenty-four groups were placed horizontally,and another twenty-four groups were placed vertically in the graphitemold. Nicrobraz LM powder (−140 mesh) (made by Wall Colmonoy Company)was added on the top of these segments. These samples were heated in avacuum furnace (10⁻⁵ torr) to 1050° C. for 20 minutes for horizontallyplaced segments, and 30 minutes for vertically placed segments. Themelted LM alloy (Ni—C—B—Si with a liquidus point at 1000° C.)infiltrated into these segments and filled the porosity. The excess LMbraze on these segments were ground by electrode discharge (EDG). Eachof the 24 segments so fabricated were brazed onto a 14 inch (diameter)circular saw blade. These blades were used to cut granite and showedmarked improvement over conventional saw blades.

Example 4

Nicrobraz LM powder was mixed with an acrylic binder and rolled to formlayers of about 0.25 mm. 40/50 mesh MBS-960 diamond grit manufactured byGeneral Electric Company was planted into these metal layers accordingto the method as illustrated in FIGS. 5A-D. These diamond planted metallayers were cut in proper size and wrapped around 2,000 beads (pearls)of wire saw. These beads (10 mm in diameter by 10 mm long) were dividedinto two groups, one contains 280 crystals (about 0.2 carat). Thesebeads were heated in a vacuum furnace to a temperature of 1,000° C. for8 minutes. These beads were mounted on several wire saws and were usedto cut marble, serpentine and granite. The performance of these beadswas found to be superior to conventional beads. The latter beads weretypically made by either hot pressing or electroplating. Theseconventional beads may contain a much higher amount of diamond (up to 1carat) per bead.

Example 5

The same method as described by Example 4, but applied to otherproducts, e.g., circular saws, thin-wall core bits, and curvaturegrounder. Each of these products shows superior performance overconventional electro-plated diamond tools having similar superabrasiveconcentrations.

Example 6

Mixture of metal powders that contain 87 wt % of −140 mesh Nichrobraz LM(made by Wall Comonoy, U.S.), 8 wt % of iron of −125 mesh, and 5 wt % ofcopper of −60 mesh were mixed with 3 wt % of an acrylic binder to form adough. The dough is rolled between two rollers to form sheets of 0.6 mmthick. Each sheet is cut to shape and covered with a template. 30/40mesh (0.420 to 0.595 mm) diamond grits of SDA-100+ grade (made by DeBeers, South Africa) were planted into the metal layers in apredetermined pattern with a diamond-to-diamond distance of about 2 mm.Three layers were stacked together and wrapped around a steel sleeve toform a diamond bead of 10 mm in diameter and 10 mm in length. Thesebeads were heated in a vacuum furnace to consolidate the metal that alsobraze the diamond in place and onto the steel sleeve. 1,000 of suchdiamond beads were fitted over 5 mm steel cable that contained 7×19wires and are spaced by plastic coating formed by injection molding. Thewire was 25 meters long and was joined end-to-end to form a loop. Thiswire saw was used to cut granite blocks (3.5 meter long by 1.8 meterhigh) of all grades. The life achieved was 0.5 square meter cut surfaceper diamond bead consumed (0.5 carat). This area cut is twice of thatcut by conventional diamond beads made by a powder metallurgical method.

Example 7

This is the same as Example 6, except many diamond impregnated layerswere assembled to form a block 20 mm long by 5 mm thick by 7 mm high.These blocks were consolidated in a vacuum furnace to form diamondsegments. Each segment contained about 8 volume percent diamond. 30 ofsuch segments were brazed onto a 4 meter long steel frame and the famewas mounted on a reciprocating sawing machine. The saw was used to cutmarble blocks and had a life more than twice as long as thanconventional diamond segments produced by powder metallurgical methods.

Example 8

This the same as Example 7, except the diamond planted layers wereassembled to form segments of about 24 mm long by 3.5 mm thick for corebits 150 mm in diameter. The diamond content in these segments was about4 volume percent. Ten of such core bits were used to drill concrete. Thedrilling speed and the life of these core bits were much higher thanconventional diamond segment bits made by powder metallurgical methods.

Example 9

This is the same as Example 8, except the shape of segments is forcircular saws. These segments were brazed to make circular saws of 230mm (with 18 segments of 40 mm by 8.5 mm by 2.4 mm), 300 mm (with 21segments of 50 mm by 8.5 mm by 2.8 mm), and 350 mm (with 24 segments of50 mm by 8.5 mm by 3.2 mm) in diameter. These saws were used to cutgranite, asphalt, and concrete with superior performance.

Example 10

This is the same as Example 7, except the segments are used as dressersfor conditioning grinding wheels.

Example 11

A single layer of 14/16 mesh (1.4 mm to 1.2 mm in size) diamond grits(natural diamond EMB-S made by De Beers) planted sheet is covered over apellet of 20 mm diameter by 8 mm thickness. Many of these pellets werebrazed in a vacuum furnace. More than 3000 of such pellets were mountedon floor grinding machines to grind stone and wood floors. The resultsindicate that the grinding speed could be three times faster thanconventional diamond grinders.

Example 12

A single layer that contained planted diamond grits of 40/50 mesh(0.420-0.297 mm size) ISD 1700 grade (made by Iljin Diamond of Korea)was laid over the curved surface of a profile wheel and brazed to form arigid tool in a vacuum furnace. More than 100 of such profile wheels ofvarious diameters were used to form the edges of granite and marbleslabs. These profile wheels were capable to cut more than 3 times fasterthan conventional diamond tools made by either electroplating orsintering method.

Example 13

This is the same as Example 12, except that the diamond planted layer iswrapped around a steel sleeve to form single layered diamond beads. Morethan 100,000 of such beads were manufactured. They were used to cutgranite or marble with superior performance.

Example 14

This is the same as Example 11, except the diamond grits were 80/100mesh, and the diamond planted layer was used to cover the surface of aflat disk 4 inches in diameter. Four such disks were produced and usedas conditioner to dress the CMP (chemical and mechanical polishing) padthat polished silicon wafers. The result indicated that the CMPefficiency was much improved and the conditioner outlasted conventionalconditioners made by either electroplating or brazing.

The above description and examples are intended only to illustratecertain potential uses of this invention. It will be readily understoodby those persons skilled in the art that the present invention issuitable for a broad utility and applications. Many embodiments andadaptations of the present invention other than those herein described,as well as many variations, modifications and equivalent arrangementswill be apparent from or reasonably suggested by the present inventionand the forgoing description thereof without departing from thesubstance for scope of the invention. Accordingly, while the presentinvention has been described herein in detail in relation to itspreferred embodiment, it is to be understood that this disclosure isonly illustrative and exemplary of the present invention and is mademerely for the purpose of providing a full and enabling disclosure ofthe invention. The forgoing disclosure is not intended to be construedto limit the present invention or otherwise to exclude any such otherembodiments, adaptations, variations, modifications and equivalentarrangements, the present invention being limited only by the claimsappended hereto and the equivalents thereof.

1. A superabrasive tool having a superabrasive impregnated segment,comprising: a metal matrix configured for bonding superabrasiveparticles; and a plurality superabrasive particles held in the metalmatrix at specific positions according to a predetermined pattern,wherein tips of each of the plurality of the superabrasive particlesprotrude from the metal matrix to a uniform height.
 2. The tool of claim1, wherein the uniform height has a variance that is less than or equalto 50 μm.
 3. The tool of claim 1, wherein the predetermined pattern is auniform pattern.
 4. The tool of claim 1, wherein the plurality ofsuperabrasive particles is diamond or cBN.
 5. The tool of claim 1,wherein the plurality of superabrasive particles is diamond.
 6. The toolof claim 1, wherein the uniform height is an equal height.
 7. A methodfor making a superabrasive tool, comprising: arranging a plurality ofsuperabrasive particles in a metal matrix at specific positions suchthat the plurality of superabrasive particles are held in the metalmatrix according to a predetermined pattern, wherein tips of each of theplurality of the superabrasive particles protrude from the metal matrixto a uniform height.
 8. The method of claim 7, wherein arranging theplurality of superabrasive particles includes: placing a template with aplurality of apertures formed therein on the metal matrix; filling theapertures of the template with superabrasive particles; pressing thesuperabrasive particles at least partially into the metal matrix; andremoving the template.
 9. The method of claim 7, wherein the template isconfigured to hold only one superabrasive particle in each aperture. 10.The method of claim 7, wherein the uniform height has a variance that isless than or equal to 50 μm.
 11. The method of claim 7, wherein thepredetermined pattern is a uniform pattern.
 12. The method of claim 7,wherein the uniform height is an equal height.
 13. The method of claim7, wherein the plurality of superabrasive particles is diamond or cBN.14. The method of claim 7, wherein the plurality of superabrasiveparticles is diamond.
 15. A method for making a superabrasive tool,comprising: providing a template with a plurality of apertures formedtherein; filling the apertures of the template with superabrasiveparticles; removing the template such that the plurality ofsuperabrasive particles are maintained at specific positions accordingto a predetermined pattern; and forming a metal matrix to hold theplurality of superabrasive particles in the predetermined pattern,wherein tips of each of the plurality of the superabrasive particlesprotrude from the metal matrix to a uniform height.
 16. The method ofclaim 15, wherein the uniform height has a variance that is less than orequal to 50 μm.
 17. The method of claim 15, wherein the template isconfigured to hold only one superabrasive particle in each aperture. 18.The method of claim 15, wherein the predetermined pattern is a uniformpattern.
 19. The method of claim 15, wherein the plurality ofsuperabrasive particles is diamond or cBN.
 20. The method of claim 15,wherein the plurality of superabrasive particles is diamond.